You're Canadian and speak English. In other words, you're at the top of the list for English teachers in Japan already.
You're young, which is also a plus for many employers.
You're interested in Japan. Another plus.
Teaching English probably is your best option, but there is other work in Japan. As you know, you'll have to learn more Japanese to have a greater choice of work in Japan.
There is a myth that some people in this forum like to keep alive, that people need a university degree to get a visa for Japan. It's just a myth. It's helpful to have one, but not necessary.
Your college education will help you in Japan.
1. Yes. 2. Yes.
You're only studying something perfect for teaching.
With that said, if you had a university degree, you could be searching for a job from Canada. You could probably even be recruited while still in Canada, then go to Japan with a visa already in hand.
Because you don't have a university degree, you've got it a bit more difficult. Your best bet is to go to Japan and be able to support yourself while looking for a job. You have 90 days on your visitor permit. That's more than enough time to find a job, but it's a long time to be supporting yourself. Basically you have to go to Japan, have a place to stay, be able to feed yourself, have some decent attire for interviews, have internet access, and just be ready to go around for interviews.
Once you're in the country, and actively looking for work, you'll find something. It's a lot easier for a company to sponsor your visa once you're in Japan. It's almost impossible for a company to sponsor your visa if you're not there yet and don't have a degree. Companies are obliged to have employees who can legally work in Japan, so although most prefer that you already have a visa, a lot will still sponsor your visa even if they don't really want to. The fact is a company that loses a teacher (happens all the time in Japan) is going to be desperate for someone to fill that position asap. Most Japanese like things to work smoothly. If one teacher leaves, they want someone new in the next day. This is where you come in.
So, yeah, it's easier with a university degree, but you've still got tons of chances for work in Japan without one. Remember, once your foot's in the door, things will get better. Spend your money on a ticket to Japan, spend a couple weeks tops looking for jobs, get a job, maybe it will suck for awhile, just deal with it, stay, earn your money back, stay, then reassess where you're at. It could be best just to stay where you are, or it might be time to move on to something else.
Also, be careful of the negativity with other foreigners in Japan, especially at the beginning when you're looking for jobs and possibly hanging out in cheap accommodation. Soon enough you'll be out of that environment.
It would be best too once you've decided to go, to check the internet as much as possible as to what kinds of jobs are available. You'll see that a lot require you to be in Japan already, but it'll give you a sense of what's out there. Also, don't take the job ads word for word. A lot of those companies deal with staff that constantly changes and they made their original job positing years ago. They just pull it out and post it whenever a teacher leaves. For example, some places will say that you need a degree and TESL qualification. They probably forgot that they even asked for that. The fact is, if you show up for an interview and they like you, you're in. Especially if they need someone asap. Once people start doing their job, managers aren't looking at who has the best qualifications anymore. They're looking at who does the job well.